1. Field of the Invention
This invention relates to idler rolls and more particularly to idler rolls used in belt conveyor systems.
2. Description of Related Art
Idler rolls are typically used in belt conveyor systems for handling bulk material, such as coal, sand, widgets, and the like. As is known in the art, a series of idler rolls may be arranged in a u-shaped fashion having a conveyor disposed thereon for carrying bulk material. For example, a first idler roll may be aligned along a horizontal direction and a second and a third idler roll may extend at an angle (i.e., 30 to 45 degrees) in the same plane as the first idler roll, forming a u-shaped configuration. A plurality of these first, second, and third idler rolls may be arranged along the desired path for moving the bulk material. When a conveyor is disposed above the plurality of idler rolls, the u-shaped configuration helps prevent the spillage of the bulk material from the conveyor itself.
Prior art idlers have been formed with steel rolls. That is, a steel roll is placed around a center shaft forming the steel idler roll. Steel idler rolls, however, tend to allow build-up of material on the roll especially where the material being transported is sticky in nature. In addition, steel idler rolls may wear faster when the materials being transported are abrasive substances.
To help overcome the disadvantages of steel idler rolls, idler rolls have also been formed with an extruded polyethylene shell. Referring to FIG. 1, there is shown an idler roll 10 having a steel shaft 12 and steel shell 14. A polyethylene shell 16 is disposed around the steel shaft 12 and shell 14 by the use of polyethylene disks 18 at each end of the idler roll 10. Air gap 20 is present in the region between the polyethylene disks 18, the steel shell 14 and the polyethylene shell 16. Because the polyethylene shell is extruded, it may be necessary to add an additional processing step of smoothing the exterior surface of the polyethylene shell 16 by a turning or smoothing operation. This adds increased manufacturing costs. In addition, because the disks 18 are disposed on each end of the idler roll 10, an absence of load support may result in the central region of the idler roll (i.e., in the location of the air gap 20).
Prior art idler rolls typically are designed having a certain length for a given application. For example, idler rolls varying in size from about a half-a-foot to about six feet are typically used for conveying bulk material. Thus, a plurality of different sized idler rolls would have to be made having varying size shells 16 to cover all of the desired lengths required. In the past, idler rolls have been formed by combining a plurality single size polyethylene shells onto a steel shell and shaft to form a larger idler roll. However, it is desirable to have flexibility to create an idler roll of a given size based upon a series of modular sections which may vary in length. This would allow for the building of an idler roll whose length is not an integral multiple of the single size polyethylene shell. Such flexibility would allow for incremental differences in the sizes of idler rolls desired. As a result, the use of modular sections may allow for less parts for forming an idler roll of a desired length to be housed.
Because typical prior art polyethylene idler rolls are formed by placing an extruded polyethylene shell on a steel shell, they have edges 22 which are perpendicular in cross section. When the u-shaped configuration noted above is formed, there may be a sharp contact point between two adjacent idler rolls and the conveyor belt disposed thereon. These sharp points may lessen the life of the conveyor belt. Therefore, it is desirable to have a polyethylene idler roll which does not have perpendicular edges for affecting the life of the conveyor belt placed thereon.